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Predation
Psychology 3106
Introduction
You hear quite a bit about foraging
Foraging is a two way street

There has to be a ‘foragee’ as well
Just as foragers have evolved strategies,
so have prey
Possible Strategies
Live in a group
Camouflage
Armour
Fight back
Don’t taste good!
Aposematism
Some insects taste
bad and are obvious
about it
Usually have a diet of
plants that does not
taste good to the
predator
The Monarch butterfly
is great example
Questions, Questions,
Questions…..
Two evolutionary questions can be asked


1) How did distastefulness evolve?
2) Why are distasteful prey so obvious about
it?
Question 1
Well, it should increase the probability of
the prey surviving
But, the predator has to sample a prey
item in order to learn that it will get sick
How does the fitness of the prey item
increase if it has been eaten?
Species level?

Not a chance in hell…..
So How then?
Well, here’s a hint: Usually aposematic
bugs are gregarious
Usually they are surrounded by siblings
If only a few of the brood are eaten then
the frequency of the distasteful gene will
spread
(Fisher, 1958) one of the first kin selection
models
Why be so obvious then?
First off, not all distasteful prey are
obvious
Most are though
Two possible explanations
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Contrast with the background makes learning
easier than learning about cryptic prey
Gibson (1974)
Blue, green or red millet on a green dot
background
Gibson (1974)
Feeding platform dropped when red
‘aposematic’ grain was eaten
The birds stopped eating red seeds, still
ate the blue and green
Can’t be the background then, as the
cryptic ones were still eaten
Gittleman and Harvey (1980)
Chicks fed two grain
types
Colour did not matter
on its own
Distastefulness and
colour are the key
Shettleworth (1972)
Chicks learned to avoid
unpalatable water if it was
a novel colour (other than
what they were raised on)
Novelty is the key, not
contrast
So, could be that the prey
evolved a strategy of
being different as
possible
Kin Selection
Aposematism must have
evolved through kin
selection
Aposematic butterflies
are gregarious
Cryptic butterflies are not!
Aposematic live longer
than cryptic

They could still ‘teach a
lesson’
Other characteristics
They have smaller territories
They roost communally
They have delayed sexual maturity
So, because they live longer they can
teach the lesson more easily
Mimicry
Some insects are
aposematic and
successful, why not
copy?

Batesian mimicry
Colouration is similar
to toxic species, but
the prey item is not
toxic
Mullerian Mimicry
In Mullerian mimicry,
all species that share
a colouration are
dangerous
Many snakes use this
Also may have
characteristics that
make prey look like a
predator!
Conclusions
Evolution is basically an arms race
As fast as aposematism or crytic
colouration evolve, species learn to detect
the prey

Learn evolutionarily or in the real sense